Automated Irrigation System with Sensors and Relays

Table of Contents🔗

• Introduction
• Components Required
• System Design and Working Principle
• Sensor-to-Relay Wiring Guide
• Arduino Code Implementation
• Testing, Calibration, and Optimization
• Scaling for Agricultural Use
• Safety and Efficiency Best Practices
• Conclusion

Introduction🔗

Automated irrigation systems transform plant care by ensuring watering occurs only when needed, preventing water waste and maintaining plant health. This project combines soil moisture sensors with relay-controlled pumps to automate watering based on real-time soil conditions. Learn to build a closed-loop control system that integrates sensors, microcontrollers, and actuators-a foundational concept in IoT and automation.

Components Required🔗

Core Components

Optional Components

• LCD Display: Visualize moisture levels and system status.
• Water Flow Meter: Track water usage (e.g., YF-S201 hall effect sensor).
• Wi-Fi Module: Enable remote monitoring (e.g., ESP8266).

System Design and Working Principle🔗

The system uses closed-loop feedback control:

1. Moisture Measurement:

2. Decision Logic:

• Dry Threshold: analogRead() ≤ 400 (parched soil)
• Wet Threshold: analogRead() ≥ 800 (saturated soil)

3. Relay Activation:

// Hysteresis prevents relay chatter
if (moisture < DRY_THRESHOLD && !pumpActive) {
  activatePump();
} else if (moisture > WET_THRESHOLD && pumpActive) {
  deactivatePump();
}

Sensor-to-Relay Wiring Guide🔗

Critical Connections

1. Soil Sensor:

• VCC → 5V
• GND → GND
• SIG → A0 (add 100nF capacitor to reduce noise)

2. Relay Module:

• IN → D8 via BC547 transistor (to handle 20mA coil current)
• Flyback diode across relay coil for voltage spike suppression.

3. Pump:

• Connect to relay's NO (Normally Open) terminal.

Arduino Code Implementation🔗

Advanced Code with Hysteresis

const int sensorPin = A0;
const int relayPin = 8;
int moisture = 0;
bool pumpActive = false;
// Calibrate per soil type
#define DRY_THRESHOLD 400
#define WET_THRESHOLD 800
void setup() {
  Serial.begin(9600);
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH); // Relay OFF initially
}
void loop() {
  moisture = analogRead(sensorPin);
  Serial.print("Moisture: ");
  Serial.println(moisture);
  if (moisture <= DRY_THRESHOLD && !pumpActive) {
    digitalWrite(relayPin, LOW); // Relay ON
    pumpActive = true;
    Serial.println("Pump ACTIVATED");
  }
  else if (moisture >= WET_THRESHOLD && pumpActive) {
    digitalWrite(relayPin, HIGH); // Relay OFF
    pumpActive = false;
    Serial.println("Pump DEACTIVATED");
  }
  delay(2000); // Prevent rapid cycling
}

Simplified Single-Threshold Alternative

const int sensorPin = A0;
const int relayPin = 8;
const int moistureThreshold = 600;
void setup() {
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW); // Pump OFF initially
}
void loop() {
  int sensorValue = analogRead(sensorPin);
  if (sensorValue > moistureThreshold) {
    digitalWrite(relayPin, HIGH); // Pump ON
  } else {
    digitalWrite(relayPin, LOW); // Pump OFF
  }
  delay(2000);
}

Testing, Calibration, and Optimization🔗

Calibration Protocol

1. Dry Calibration:

• Insert sensor in dry soil. Record analog value as DRY_THRESHOLD.

2. Wet Calibration:

• Submerge sensor in water (avoiding electrodes). Record as WET_THRESHOLD.

Troubleshooting Table

Optimization Tips

• Data Logging: Add an RTC module to track watering schedules.
• Remote Monitoring: Use ESP8266 with Blynk:

Blynk.virtualWrite(V1, moisture); // Push to dashboard

• Energy Savings: Implement sleep mode:

#include <LowPower.h>
LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);

Scaling for Agricultural Use🔗

• Multi-Zone Control: Use Arduino Mega with 8 relays/sensors.
• Water Flow Tracking: Integrate YF-S201 sensor:

volatile int pulseCount;
void pulseCounter() { pulseCount++; }
attachInterrupt(digitalPinToInterrupt(2), pulseCounter, FALLING);

Safety and Efficiency Best Practices🔗

1. Waterproofing: Pot sensor electronics in epoxy resin.

2. Power Isolation: Use separate 12V supply for the pump.

3. Maintenance: Weekly sensor validation with gravimetric soil tests.

Conclusion🔗

This automated irrigation system demonstrates the power of closed-loop control in real-world applications. By integrating sensors, microcontrollers, and relays, you can create a water-efficient solution adaptable to home gardens or agricultural fields. Experiment with thresholds, expand with IoT capabilities, and refine the design for your specific needs. Whether you're a hobbyist or a professional, this project offers valuable insights into electronics, programming, and sustainable technology.